Centor score: how the four strep throat criteria are counted

The Centor score gives 1 point each for four findings in a person with a sore throat: tonsillar exudates, tender anterior cervical (neck) nodes, a history of fever, and no cough. The total runs from 0 to 4. The plain Centor score has no age item; the age-adjusted version is the McIsaac score.

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McIsaac WJ et al. · 2004
The Centor formula
Worked examples
Frequently asked questions

What is the Centor score?

Robert Centor and colleagues described the four findings in 1981. Their paper studied adults who came to an urban emergency room with a sore throat, and their model for a positive throat culture used four variables: tonsillar exudates, swollen tender anterior cervical nodes, lack of a cough, and a history of fever.

Warren McIsaac and colleagues later added an age adjustment. Their 2004 paper in JAMA calls it the modified Centor score; it's also known as the McIsaac score. Magent's calculator does both, and you have to choose one: it doesn't pick the edition for you.

This page is mostly about the plain Centor score, with McIsaac's version alongside for comparison. It explains the arithmetic. It doesn't give a cutoff, and it doesn't say what a score means for a particular person.

The Centor formula

Centor = tonsillar exudates (1)
       + tender anterior cervical nodes (1)
       + history of fever (1)
       + cough absent (1)
maximum = 4

With the Centor edition, the calculator returns this expression:

Centor = tonsillar_exudates + tender_anterior_cervical_nodes + history_of_fever + cough_absent; each 1 if present; max 4

The McIsaac edition uses the same four findings and adds age. This is the exact expression stored in the calculator's record, which is written for the McIsaac edition:

McIsaac = Centor criteria + age 3-14 +1, 15-44 0, >=45 -1; max 5

What each part means

Input	Finding	Points
`tonsillar_exudates`	Exudates (white patches or pus) on the tonsils	1
`tender_anterior_cervical_nodes`	Tender lymph nodes at the front of the neck	1
`history_of_fever`	A history of fever	1
`cough_absent`	No cough (true when cough is absent)	1

How the score works

Check the four findings. Each one that's present adds 1 point.
Watch the cough item. It scores when cough is absent, not when it's present.
Add them up. The Centor total is 0 to 4. Age doesn't change it.

Centor and McIsaac side by side

The McIsaac edition starts from the same four points, then adjusts for age:

Age 3 to 14: add 1.
Age 15 to 44: add nothing.
Age 45 or older: subtract 1.

So the McIsaac total runs from −1 to 5. The calculator takes age from 3 to 120 for McIsaac and ignores age for Centor.

Inputs come from the user

The record says the four findings are true/false answers from the person using the calculator. Magent's calculator doesn't examine the throat. It returns the total, the maximum for the chosen edition, the edition, a line for each finding, and for McIsaac the age it used.

Worked examples

These use Magent's own expected values for the calculator.

Example 1: Centor, no findings

Tonsillar exudates, tender nodes, fever and no cough are all false.
Score: 0 + 0 + 0 + 0 = 0 out of 4.

Example 2: Centor, all four findings

Tonsillar exudates → 1; tender anterior cervical nodes → 1.
History of fever → 1; cough absent → 1.
Score: 1 + 1 + 1 + 1 = 4 out of 4.

Example 3: McIsaac, age 8, no findings

The four findings add 0.
Age 8 is in the 3 to 14 group → +1.
Score: 0 + 1 = 1 out of 5.

Example 4: McIsaac, age 30, no findings

The four findings add 0.
Age 30 is in the 15 to 44 group → 0.
Score: 0 + 0 = 0 out of 5.

Example 5: McIsaac, age 50, no findings

The four findings add 0.
Age 50 is 45 or older → −1.
Score: 0 − 1 = −1.

Examples 1 and 5 have the same findings. The Centor edition gives 0; the McIsaac edition at age 50 gives −1.

History of the Centor score

The four findings come from Centor RM, Witherspoon JM, Dalton HP, Brody CE and Link K, writing in Medical Decision Making in 1981 (volume 1, issue 3, pages 239–246).

The age-adjusted version is McIsaac's. Magent's record cites McIsaac WJ, Kellner JD, Aufricht P, Vanjaka A and Low DE, Empirical validation of guidelines for the management of pharyngitis in children and adults, JAMA, 2004 (volume 291, issue 13, pages 1587–1595).

McIsaac and colleagues first described an age-appropriate sore throat score for children and adults in CMAJ in 1998 (volume 158, issue 1, pages 75–83).

When it's used

The 1981 paper studied adults with a sore throat. The 2004 McIsaac paper studied children and adults with an acute sore throat at a family medicine clinic. Fine and colleagues validated the Centor and McIsaac scores in a large group in 2012, and the 2012 Infectious Diseases Society of America guideline by Shulman and colleagues covers group A streptococcal pharyngitis; both are listed under Further reading.

Where it's used

The 1981 paper was set in an urban emergency room. The 2004 paper was set in a family medicine clinic. Every input is a bedside finding, plus age for McIsaac.

Who uses it

The person using the calculator decides whether each finding is present. The calculator does the adding.

Limits of the calculation

It adds up four findings. It doesn't confirm or rule out strep throat, and it isn't a protocol for testing or prescribing.
The plain Centor score has no age item. If you want age counted, that's the McIsaac edition.
You choose the edition; the calculator won't choose it for you.
This page doesn't say what to do with a score.

Clinical decisions belong to a qualified clinician who knows the patient.

McIsaac score (modified Centor): the same calculator with the McIsaac edition. It adds 1 for age 3 to 14 and subtracts 1 for age 45 or older, so its maximum is 5.
CURB-65 is a separate score for community-acquired pneumonia. It doesn't use throat findings.

Glossary

Tonsillar exudates: white patches or pus on the tonsils.
Anterior cervical nodes: lymph nodes along the front of the neck.
Group A streptococcus: the bacterium behind strep throat.
Pharyngitis: inflammation of the throat.

Common mistakes

Scoring cough instead of no cough. The point is for cough being absent.
Adding an age point to the Centor score. Age belongs to the McIsaac edition.
Forgetting the McIsaac minus. At 45 or older, McIsaac subtracts 1, so a total can be −1.
Mixing the two maximums. Centor tops out at 4; McIsaac at 5.

Source

Centor RM, Witherspoon JM, Dalton HP, Brody CE, Link K. Med Decis Making. 1981;1(3):239-246. DOI: 10.1177/0272989X8100100304. PMID: 6763125

McIsaac WJ, Kellner JD, Aufricht P, Vanjaka A, Low DE. Empirical validation of guidelines for the management of pharyngitis in children and adults. JAMA. 2004;291(13):1587-1595. DOI: 10.1001/jama.291.13.1587. PMID: 15069046

Frequently asked questions

How do you calculate the Centor score?

Give 1 point each for tonsillar exudates, tender anterior cervical nodes, a history of fever, and no cough. Add them up for a total of 0 to 4.

What Centor score means strep throat?

This page doesn't give a cutoff. The score adds up four findings; what a score means depends on the person and the clinical context.

Is the Centor score adjusted for age?

No. The plain Centor score has no age item. The McIsaac score (the modified Centor score) adds 1 for age 3 to 14 and subtracts 1 for age 45 or older.

What is the highest Centor score?

The highest McIsaac score is 5.

Can the McIsaac score be negative?

Yes. Someone 45 or older with none of the four findings scores −1.